Emulsion type practical examples

Practical situations are not always so simple, and one may encounter multiple emulsions such as double emulsions, that is, emulsions that are oil-in-water-in-oil (O/W/O) or water-in-oil-in-water (W/O/W). For example, O/W/O denotes a double emulsion containing oil droplets dispersed in aqueous droplets that are in turn dispersed in a continuous oil phase. The double emulsion droplets can be quite large (tens of micrometres) and can contain many tens of droplets of the ultimate internal phase. Developments in and applications of double emulsions have been reviewed by Garti and Bisperink [69]. There can even be more complex emulsion types [33]. Figure 1.2 shows an example of a crude oil W/O/W/O (water-in-oil-in-water-in-oil) emulsion. The type of emulsion that is formed depends on a number of factors. 

Electrostatic and non-electrostatic biopolymer complexes can also be used as effective steric stabilizers of double (multiple) emulsions. In this type of emulsion, the droplets of one liquid are dispersed within larger droplets of a second immiscible liquid (the dispersion medium for the smaller droplets of the first liquid). In practice, it is found that the so-called direct water-in-oil-in-water (W/O/W) double emulsions are more common than inverse oil-in-water-in-oil (O/W/O) emulsions (Grigoriev and Miller, 2009). In a specific example, some W/O/W double emulsions with polyglycerol polyricinoleate (PGPR) as the primary emulsifier and WPI-polysaccharide complexes as the secondary emulsifying agent were found to be efficient storage carriers for sustained release of entrapped vitamin Bi (Benichou et al., 2002). 

This book provides an introduction to the colloid and interface science of three of the most common types of colloidal dispersion emulsions, foams, and suspensions. The initial emphasis covers basic concepts important to the understanding of most kinds of colloidal dispersions, not just emulsions, foams, and suspensions, and is aimed at providing the necessary framework for understanding the applications. The treatment is integrated for each major physical property class the principles of colloid and interface science common to each dispersion type are presented first, followed as needed by separate treatments of features unique to emulsions, foams, or suspensions. The second half of the book provides examples of the applications of colloid science, again in the context of emulsions, foams, and suspensions, and includes attention to practical processes and problems in various industrial settings. 

The examples of colloids listed in Table 10.2 may be considered simple colloids because they involve one fairly distinct type of dispersed and continuous phase. In practice, many colloidal systems are much more complex in that they contain a variety of colloidal types, such as a sol, an emulsion (or multiple emulsions), an association colloid, macromolecular species, plus the continuous phase. Such systems are often referred to as complex or multiple colloids. As we shall see, even the simplest colloids can be quite complex in their characteristics. It should be easy to understand, then, why the difficulty of understanding a multiple colloid increases dramatically with the number of components present. 

There are several types of surfaces or interfaces that are of great practical importance and attracting fundamental interest. These general classifications include liquid-gas, liquid-liquid, liquid-solid, solid-gas, and solid-solid interfaces. Many examples of interfaces of natural and technological importance are available, for instance, oil-water interfaces in emulsions, air-water interfaces in foams, solid-gas interfaces in gas chromatography, and solid-water interfaces in cleaning systems [1]. 

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